So basically
Science: your best friends starting from today is the Cognito website and freesciencelessons guy from YouTube. Use the website to learn the content (what I did was start with the topic which i found the hardest and learn its content) and use freesciencelessons as you wish (i mainly used him to revise for the required practicles and other stuff)
Don't forget to do your past exam question after you finished the topics in Cognito, even if you finished subtopics doing the exam questions really helps to reinforce the information in your brain and help develop exam techniques. (you dont have to do a whole exam paper, just search up exam questions related to that one particular topic)
Maths: you can use Cognito for this but i personally think its a waste of time, i used past exam papers to practice (use ExamQ to find specific questions) and if you dont understand a question you can always just search the paper up on youtube and watch a a guy explaining the whole paper.
English: use youtube for this, MrEverythingEnglish is absolutely amazing, watch his past GCSE live streams which includes mostly the vital stuff u need but also some unqiue stuff (idk if they are still there), but his videos in general are super useful. Also use MrSalles he is good as well. Do practice questions and get them marked by your teacher, ask for feedback!!!!
History: i really dont know how i got through this subject but do exam questions and get them marked by your teacher.
Im not too sure about the rest, plus i dont know much about flashcards as i didnt use them a lot. But stay consistent with your revision (do 2-3 hours a day if possible, but everyone has their own sweet-spot with revision time) and get some sleep!
btw im not suggesting these are the only revision methods that you should use, use this as a base to create a combination which suits you and gets you your 9s.
Hopefully this helped!